Deep Dark Chocolate Cupcakes with Classic Chocolate Frosting (without powdered sugar)

I don't have enough words to describe how good these cupcakes are!  They're chocolaty, velvety, fluffy, melt-in-your-mouth, absolutely amazing!  And the frosting is to die for!  Super creamy, not too sweet, definitely chocolaty!  Best cupcakes ever!  Enjoy!
Ingredients (this makes and frosts 24 regular cupcakes AND 24 mini cupcakes):
For cupcakes:
-1 cup unsweetened cocoa powder
-2 cups very hot water
-4 tsp vanilla extract
-3 stick unsalted butter, at room temperature
-2 1/2 cups sugar
-4 large eggs, at room temperature
-2 1/2 cups flour
-1 tsp baking soda
-1 tsp salt
For frosting:
-1/2 cup flour
-3 Tbs unsweetened cocoa powder
-2/3 cup granulated sugar
-1 cup milk
-1 cup semi-sweet chocolate chips
-2 stick unsalted butter, at room temperature
Adjust the oven rack to the the middle position.  Preheat the oven to 350 F.  Line muffin pans with cupcake liners and set aside.
Put the cocoa powder into a bowl.   Add the hot water and mix until smooth.  Cool to room temperature, then add the vanilla and mix well.  Set aside.
In your mixer's bowl, cream the butter until smooth.  Add the sugar and mix until fluffy (2-3 minutes).  Add the eggs, one at a time and beat until fluffy.  Add half of the flour and mix well.  Stir in the baking soda, salt and cocoa mixture.  Add remaining flour and mix well, scraping the sides of the bowl once in a while.  Beat until mixture looks satiny.  
Pour in prepared pans (fill about 80 % up).  Bake in preheated oven for about 20 minutes for the regular cupcakes and 10 minutes for the mini ones, or until toothpick comes out clean.
Cool for 10 minutes in the pan, then transfer to wire racks to cool completely.
While the cupcakes cool, make the frosting.
Mix the flour, cocoa powder, sugar and milk in a sauce pan, over medium heat.  Whisk until well incorporated.  Bring to a simmer and cook for 3-5 minutes, whisking continually.  Do not get distracted and burn it!  You really have to whisk it all the time!  Once it reaches the consistency of pudding and you can see the bottom of the pan while whisking, it's done.  Remove from the heat and let it cool completely (this will probably take one hour or so).
When that mixture is cooled, melt the chocolate chips.  Set aside.
In your mixer's bowl, cream the butter until fluffy (about 2 minutes).  Turn the mixer off and add the cooled flour mixture.  Beat until fluffy (about 2 minutes), scraping the sides of the bowl once in a while.  Add the melted chocolate chips and beat for another 2 minutes, until smooth and fluffy.  
Place in piping bag and decorate the cupcakes.  Enjoy!